Table 2. Lung-Function and Allergy-Test Results, According to Ventilation Group.*.
| Result | No. of Participants with Result† | Conventional Ventilation (N = 121) | HFOV (N = 127) | Adjusted Difference (95% CI)‡ | P Value |
|---|---|---|---|---|---|
| FEF z score | |||||
| FEF75 | 248 | −1.19±0.80 | −0.97±0.95 | 0.23 (0.02 to 0.45) | 0.04 |
| FEF50 | 248 | −1.37±0.85 | −1.07±0.93 | 0.30 (0.09 to 0.52) | 0.006 |
| FEF25 | 248 | −1.16±0.95 | −0.84±0.90 | 0.29 (0.07 to 0.51) | 0.01 |
| FEF25–75 | 231 | −1.58±1.05 | −1.34±1.09 | 0.21 (−0.04 to 0.47) | 0.10 |
| FEV1 z score | 248 | −0.95±1.02 | −0.60±1.08 | 0.35 (0.09 to 0.60) | 0.008 |
| FVC z score | 248 | −0.44±0.89 | −0.29±1.05 | 0.13 (−0.10 to 0.37) | 0.27 |
| FEV1:FVC ratio z score | 248 | −1.75±1.78 | −1.16±1.75 | 0.58 (0.16 to 0.99) | 0.007 |
| PEF — % of predicted | 247 | 80.3±15.0 | 86.3±15.5 | 5.85 (2.21 to 9.49) | 0.002 |
| Gas transfer | |||||
| DLCO z score | 210 | −1.10±0.92 | −0.81±1.19 | 0.31 (0.04 to 0.58) | 0.02 |
| VA (liters) | 210 | 3.44±0.66 | 3.40±0.59 | −0.05 (−0.20 to 0.09) | 0.48 |
| DLCO/VA (mmol/min/kPa/liter) | 210 | 1.73±0.20 | 1.76±0.21 | 0.04 (−0.01 to 0.09) | 0.11 |
| Residual volume z score | 211 | 0.46±1.19 | 0.31±1.35 | −0.09 (−0.42 to 0.24) | 0.60 |
| Total lung capacity z score | 213 | 0.20±1.00 | 0.36±1.13 | 0.16 (−0.12 to 0.43) | 0.26 |
| FRC z score | |||||
| FRCpleth | 218 | −0.07±1.26 | −0.11±1.28 | −0.08 (−0.41 to 0.25) | 0.63 |
| FRCHe | 229 | −0.62±1.10 | −0.75±1.05 | −0.18 (−0.44 to 0.08) | 0.19 |
| Vital capacity z score | 213 | −0.50±0.88 | −0.17±1.09 | 0.31 (0.05 to 0.57) | 0.02 |
| Respiratory resistance — % of predicted | |||||
| At 5 Hz | 237 | 99.6±23.2 | 92.5±20.9 | −7.1 (−12.5 to −1.8) | 0.009 |
| At 20 Hz | 237 | 95.5±23.8 | 90.2±22.1 | −5.2 (−10.7 to 0.2) | 0.06 |
Plus–minus values are means ±SD. CI denotes confidence interval, DLCO diffusing capacity of the lung for carbon monoxide, FEF forced expiratory flow (with FEF25, FEF50, and FEF75 indicating 25%, 50%, and 75%, respectively, of the expired vital capacity), FRCHe functional residual capacity with the use of a helium-dilution technique, FRCpleth functional residual capacity as assessed by means of plethysmography, FVC forced vital capacity, PEF peak expiratory flow, and VA alveolar volume.
Lung-function values were missing for the following measures: FEF25–75 for 10 participants in the conventional-ventilation group and 7 in the HFOV group, PEF for 1 in the conventional-ventilation group, DLCO and VA for 14 in the conventional-ventilation group and 24 in the HFOV group, residual volume for 15 and 22, respectively, total lung capacity for 14 and 21, respectively, FRCpleth for 14 and 16, respectively, FRCHe for 8 and 11, respectively, vital capacity for 14 and 21, respectively, and respiratory resistance at 5 Hz and at 20 Hz for 5 and 6, respectively.
The differences in z scores are presented as HFOV group − conventional-ventilation group, with adjustment for birth weight, gestational age, and whether surfactant had been administered. The differences in percentages are presented as mean percentage points (HFOV group – conventional-ventilation group), with adjustment for birth weight, gestational age, and whether surfactant had been administered before birth.